MIG (metal-in-gap) magnet heads have been developed and are particularly suitable for recording of video signals on high coercive tapes, such as metal particle tapes (MP-tapes) or vaporized metal tapes (ME-tapes), due to their magnetic characteristics. The basic structure of a head surface of such a magnetic head is by way of illustration shown in FIG. 1. As illustrated, the operational magnetic gap Sp of the head is surrounded on both sides by a soft magnetic layer, preferably made from a sendust alloy S (Fe-Al-Si), a material which has a high permeability or saturation induction. The sendust alloy S is applied to the respective core halves, which are made of ferrite F, by evaporation or sputtering, with the respective core halves having been provided with an adhering layer (not illustrated).
It is known that in such arrangements, pseudo gap effects occur at the border faces between the ferrite F and the sendust alloy S, which cause undesirable maxima and minima in the play back voltage.
In an attempt to avoid such pseudo gap effects tiltedsendust-sputtered-ferrite heads (TSS-heads) were developed wherein the border faces between the ferrite and the sendust alloy extend at an angle of, for example, 45.degree. with respect to the gap. This results in reducing these pseudo gap effects to negligibly small amounts. Such TSS heads are illustrated in German application No. DE-OS 34 47 700.
As disclosed in this reference (see for example FIG. 49) , there is provided a magnetic head having an operational magnetic gap g bounded or surrounded on both sides by a soft magnetic layer made of a sendust alloy designated 74 A and B. The border lines or faces between the sendust alloy and the core material made of ferrite 70 and 71 at 70A and 71A extend in a predetermined angle with respect to the gap direction. In addition, non-magnetic glass inserts 72A, and 72B and 73 are provided as a connecting material in the gap area between the two core halves. Since in the known head the sendust layers are exclusively mounted in the gap area and do not extend into the inference or lower area (i.e., not into the area disposed "below" the winding space 75 illustrated in FIG. 49 thereof), an accurate adjusting in the lower area is not required when making the heads. Also, the spatial expansion of the layer to be sputtered thereon is relatively low so that a considerable saving of time is achieved during manufacturing. This is in contrast to the making of magnetic heads wherein the sendust layer extends into the inference or lower area (as for example as set forth in German application No. DE-OS 34 47 700 at FIG. 1, the metal film 2).
With regard to this latter type head, a method for making it is described with respect to FIGS. 42 to 48 of said reference. In this regard, a square shaped ferrite block 40 is provided as a base material for the manufacturing process. A plurality of grooves 42 are ground then into the surface of this ferrite block. These grooves are then filled with molten glass which is designated 43A. Thereafter, the upper side 41 and the front side 44 of ferrite block 40 are ground smooth. A plurality of further grooves 45 are ground into the ferrite block in the next operating step which have a larger width than what is to be the track width. Into these further grooves 45, a thin sendust film is sputtered such that the thickness of the sendust film on the inner sides 46 of grooves 45 will correspond to the desired track width. Thereafter, the grooves 45 are filled with molten glass 49 (see FIG. 46). The upper side 41 and the front side 44 of the block 40 are then ground smooth. A groove 61 (winding space) is provided in the block intended for receiving the winding which thereafter is subsequently mounted. The block made in this manner is designated therein by the number 60.
In the next operating step, the blocks 40 and 60 are placed adjacent to each other and are connected with each other by means of molten glass. The total block which is obtained in this manner is separated along lines A--A and A'--A' for forming individual heads. Finally, the surfaces of the individual heads which are in contact with the magnetic tape are ground and polished.
However, there is a disadvantage to this method. Firstly, the pre- and post-grinding of the ferrite block is expensive. For example, for making n magnetic heads the grinding of 2n "glass"-grooves 42 is required. In addition, care has to be taken that during the sputtering of the sendust alloy on the inside of the grooves 46, the thickness of the sputtered layer corresponds exactly to the track width. This in turn means a high requirement concerning accuracy and requires a constant control or measuring of the thickness of the sputtered on layer. Moreover, the danger exists in this sputtering process that the sputtered sendust layer may peel off from the inner side of groove 46. Accordingly, there exists a need to provide for the manufacture of MIG magnetic heads which avoids the aforenoted disadvantages.